Your PC uses how many Kilowatts per month?

The forum for non-component-related silent pc discussions.

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee

Post Reply
NetTechie
Posts: 343
Joined: Sun Mar 07, 2004 6:58 am
Location: USA

Your PC uses how many Kilowatts per month?

Post by NetTechie » Fri Sep 03, 2004 11:51 am

Using Kill-A-Watt I'm going to try to determine the Kilowatts my system uses per month... has anyone else done this? If so, how many does your system use per 24 hours average?

hvengel
Posts: 205
Joined: Sat Oct 19, 2002 12:06 am
Location: Concord, Ca

Post by hvengel » Fri Sep 03, 2004 12:04 pm

Typical PC consumes 85 to 150 watts. So do the math (24 x 85)/1000 and (24 X 150)/1000 will give the per day KW useage for an 85 watt and a 150 watt PC. So between 2.04 and 3.6 KW per day. So depending on what your electrical rates are that would be $0.16 to $0.60 per day.

My PC consumes 204 watts if I include the monitors and about 85 watts with out the monitors.
Hal

mpteach
Posts: 426
Joined: Mon Dec 22, 2003 8:14 pm
Location: CT USA
Contact:

Post by mpteach » Fri Sep 03, 2004 12:18 pm

Alot of people at SPCR have kill-a-watt meters, it would be nice if somebody wrote up a good review on them, maybe even compared their accuracy to the new stylish seasonic power-angel.

Copper
*Lifetime Patron*
Posts: 587
Joined: Sun Feb 22, 2004 8:43 am

Post by Copper » Fri Sep 03, 2004 3:56 pm

My 3.0C system, undervolted to 1.4000 Vcore, is pulling 76 watts, or about 1.8 KWHs per day running dual instances of SETI 24/7. The same system underclocked to 2.0 ghz and undervolted to .9500 pulls just 35 watts running SETI.

Prozzaks
Posts: 32
Joined: Thu Mar 25, 2004 12:28 pm
Location: Sherbrooke, QC, Canada

Mesured PC Power

Post by Prozzaks » Tue Sep 14, 2004 6:08 am

I build myself a jig that allows me to safely measure the Power used by any appliance. I basically use 2 multimeter : One plugged in parallel to measure voltage the other one plug in series to measure the current.

I got the following results for my PC:

Antec Sonata ( Included 380 W Power supply )
ASUS A7N8X-E Deluxe
Athlon XP 2500+ ( Barton 166 MHz DDR FSB )
2x Kingston HyperX 256MB KHX2700/256 ( DDR 333MHz (PC2700) )
MSI GeForce3 Ti200 64MB ( Home build cooling fan and bracket )
Creative Labs SoundBlaster Live 5.1
Adaptec SCSI Host Adapter AHA2940
Pioneer DVR-107D ( DVD±RW 8X )
Pioneer DVD-117
Western Digital WD800JB 80GB 8MB Cache

During the time I took all the reading, the voltage stayed pretty stable at 126 V.

Power ( Watts ) = Voltage ( Volts ) * Current ( Amperes )

While idling at my Linux or Windows desktop, I measured 0,9 A which give a power of 113.4W

I tried playing various games ( UT2004 Linux, Return to castle Wolfenstein Linux, Ghost Recon, NOLF2, Vice City )

While playing most games, the current would fluctuate lightly between 1,04 and 1,07 giving respectively 131.04W and 134.82.

I was really surprised when I tried Vice City! The current fluctuates a lot depending on what is happening in the game! Just staying still a corner or driving around "normally" I measured 0,96A ( 120.96W ) I then decided to see how much I could load the game, so I went on a rampage and fired at everything until I had the entire police force and army after me. The power then rose to 1,03A ( 129.78W ) but it didn't stay that high for to long. As soon as things coled down in the game, the current dropped back to 0.96A.

I then decided to try a little test that would only load the processor and not the graphic card, so I booted linux and used the following command : cat /proc/kcore | bzip2 -9c > /dev/null. For those who are not familiar with unix, it basicly reads the entire system memory, compresses it and discards the result. ( pretty good for wasting all your CPU cycles ;) While it was running, I measured a current of 1,07A which lead me to the following conclusion : The thing that influences the power draw the most is the CPU usage. That leaves only to possibility for the video adapter : I draws a lot no matter if it's working or idle, or doesn't draw much anyhow. Using my fingers as thermal probes, I was able to feel the temperature of the video card rising when it was under load.

Since the amount of heat dissipated by a computer component is pretty much in direct relation with the powers it draws, it suggests that the video adapter draw gets bigger under load. I have not collected sufficient data to be able to nail down the impact of the GeForce3 Ti200 on the entire system power draw.

When the HD went in sleep mode ( spin down ) the system power was reduced by ~10W.

I tested the load generated by using the network and optical drives, but don't remember the figures. However, I do remember that it was nowhere near what the CPU was able to draw.

I then thought about cpuburn... 3v!| I tried the different versions under Linux and the K7 version was the one that generated the greatest load. A whopping 1.2A! That's 151.2 Watts! I was never able to go over 1,07A with "regular" system use. It confirms my theory that the CPU is the greatest power sucker.

Further tests should include testing the system without the display adapter, testing while undercloking the CPU and testings with all the drives unplugged.

I measured the power used by my monitor Viewsonic G773 ( 17" ). The brighter the image the more power it used. It maxed out around 100W which is the maximum rated value.

I hope my results will help you guess your system power requirements, and as soon as will have some spare time, I will do further testing.

p.s. : Sory for all he mistakes, I don't write this much in English often anymore.

ChrisH
Friend of SPCR
Posts: 65
Joined: Wed Oct 30, 2002 10:44 am
Location: Charlotte, NC USA - Go Panthers!

Re: Mesured PC Power

Post by ChrisH » Tue Sep 14, 2004 9:07 am

Prozzaks wrote:Power ( Watts ) = Voltage ( Volts ) * Current ( Amperes )
I don't think you are actually measuring Watts used by your PC. You are measuring the apparent power. This formula only works if the current and voltage are in phase as in a DC circuit. Does your power supply have active power factor correction? If it does, then the calculation should be correct. If not, then the actual power used by your PC will be lower.

Prozzaks
Posts: 32
Joined: Thu Mar 25, 2004 12:28 pm
Location: Sherbrooke, QC, Canada

AC power

Post by Prozzaks » Tue Sep 14, 2004 9:58 am

I do not know if my power suply has active power factor correction.

But isn't the formula valid if I use the effective AC values?

During my tests, I waited until the readings stabilized on my multimeters.

I don't know to much about AC current, but I remember somone told me that if I used effective readdings and that they were stable that it was called "continious regime" and the formula was correct.

Is that right or are the results wrong?

interpellated
Posts: 20
Joined: Fri Jul 30, 2004 7:21 pm

Post by interpellated » Tue Sep 14, 2004 12:19 pm

A little off the topic, but does anyone know if putting the computer into 'Stand By' mode makes a great difference in terms of power consumption, excluding a monitor's power consumption which can be powered off easily.

Thanks.


PS Prozzaks, very informative post, thank you.
-Antec Sonata case - Seasonic S12-430 -AthlonXP 3000+ -Zalman CNPS7000A-Cu w/Nexus 92mm fan -Asus A7N8X-E DLX -512 x 2 Corsair XMS -Asus Radeon 9600XT

MikeC
Site Admin
Posts: 12283
Joined: Sun Aug 11, 2002 3:26 pm
Location: Vancouver, BC, Canada
Contact:

Post by MikeC » Tue Sep 14, 2004 12:25 pm

Prozzaks --

Kudos on your power measurement experiments. :)

The Antec 380S does not have PFC, IIRC; unfortunately, I did not measure PF in my review ( http://www.silentpcreview.com/article61-page1.html ). I do know it does not have active PFC for sure; it may not have any.

<< goes to PSu test rig, pulls out an Antec 380 & runs a quick load test at 90WDC >> This test showed 0.7 PF.

What the above mean is that your real power draw is lower than what you measured. What you measured was VA. Apply PF (multiply by 0.7) to obtain true power (W).
Mike Chin, SPCR Editor/Publisher
Support SPCR by buying your gear through this link: Amazon

Tibors
Patron of SPCR
Posts: 2674
Joined: Sun Jul 04, 2004 6:07 am
Location: Houten, The Netherlands, Europe

Post by Tibors » Tue Sep 14, 2004 12:35 pm

I have bought a Sonata this spring in the EU. On the side label it says:
Antec True 380SP 380W Max With PFC
It is a version with SATA powerconnectors.

I think the P in the type is for PFC.
3) MSI RS480M2-IL | A64 3000+ | Freezer 64 | SS-301HT | 7200.7 PATA 40GB
5) Intel D525MW | Intel 320 40GB | Vertex II 180GB

MikeC
Site Admin
Posts: 12283
Joined: Sun Aug 11, 2002 3:26 pm
Location: Vancouver, BC, Canada
Contact:

Post by MikeC » Tue Sep 14, 2004 1:06 pm

Tibors wrote:I have bought a Sonata this spring in the EU. On the side label it says:
Antec True 380SP 380W Max With PFC
It is a version with SATA powerconnectors.

I think the P in the type is for PFC.
PFC = Power Factor Correction. But it is likely passive; with passive PFC, you rarely get much better than ~ 0.75 PF. My guess is they 380S may have had it before but they've only started to promote this recently.
Mike Chin, SPCR Editor/Publisher
Support SPCR by buying your gear through this link: Amazon

Prozzaks
Posts: 32
Joined: Thu Mar 25, 2004 12:28 pm
Location: Sherbrooke, QC, Canada

Post by Prozzaks » Wed Sep 15, 2004 5:01 am

Thank you for all your answers. I'm googling to find more about, VA, PF, PFC and active PFC.

As time allows I will do more tests considering the PF that MikeC gave me.

Prozzaks
Posts: 32
Joined: Thu Mar 25, 2004 12:28 pm
Location: Sherbrooke, QC, Canada

What is PFC

Post by Prozzaks » Wed Sep 15, 2004 5:56 am

With a little googling, I found the following article that explains what is Power Factor and how to correct it.
http://www.ecmweb.com/mag/electric_primer_power_factor/

So basically, the power I meseared is called Apparent Power.
Apparent power is the total energy consumed by a load or delivered by the utility.
Active power, also known as working power, is the energy converted into useful work.
The power not converted into useful work is called reactive power. You need this power to generate the magnetic field in inductors, motors, and transformers.
Another article http://home.earthlink.net/~jimlux/hv/pfc.htm helped me understand where the reactive power was spent.
The current through the reactive component (Ireactive) dissipates no power, and neither does it register on the watt hour meter. However, the reactive current does dissipate power when flowing through other resistive components in the system, like the wires, the switches, and the lossy part of a transformer (Rline). Switches have to interrupt the total current, not just the active component. Wires have to be big enough to carry the entire current, etc. Correcting the power factor reduces the amount of oversizing necessary.
However, there are some loads which draw distinctly non-sinusoidal currents. The most recently notorious is the switching power supply in a PC. These power supplies start with a bridge rectifier feeding a capacitor, and so, particularly at part load, draw their current in little peaks, when the instantaneous line voltage is above the capacitor voltage, forward biasing the rectifier.
According to what I read, it means that the power can not be corrected with a simple capacitor. Since your power isn't drawn as a clean sinusoidal, you have to supply the reactive current a the right times.

I'm guessing that it's what Active Power Correction does...

And that is exactly what it does! This Sea Sonic page explains what's PFC and what it does in the world of cuputer PSUs.

Therefore with a PF of 70% I'm guesing that the Antec True Power 380 only does passive power correction. Well... it's better than nothing but you can be sure that the next PSU I will buy will have active PFC!

Post Reply